Coating compositions of the type specified are known, for example, from EP 1171530 A1. They are used in general as cathodically depositable electrodeposition primers. EP 1171530 A1 describes electrodeposition primer compositions which yield coatings having very few disruptive craters at the same time as good adhesion of subsequent paint films. The reduction in the number of craters is achieved through the addition of homopolymers or copolymers based on polyvinylpyrrolidone, where a very wide variety of monomers can be used as comonomers. A particularly good anticrater effect is attained by polymers having a molecular weight>200 000.
EP 0358221 A2 describes electrodeposition coating solution compositions that yield coatings having very few disruptive craters in tandem with unaltered good impact strengths, adhesion of subsequent paint films, and surface qualities. For this purpose polymer microparticles are added as anticrater agents to the coating composition. The polymer microparticles have a size of 0.01 to 10 μm and can be prepared in the form of homopolymers or copolymers. The size distribution of the microparticles has a large influence on the anticrater effect. A particularly good anticrater effect is achieved in the case of bimodal or multimodal distribution of the particle sizes, i.e., when two or more microparticle populations having different particle sizes are combined.